DISTRIBUTED CONTROL SYSTEM

Session: 2009 – 2010A Seminar Report submitted to

Rajasthan Technical University, Kota (Raj.)Towards Partial Fulfillment of Degree of

Bachelor of Engineering

Submitted to: Submitted by: Vikas Jain DESAI MANAN(Electrical Dept.)

Department of Electrical EngineeringShrinathji Institute of Technology & Engineering, Nathdwara

[Approved by AICTE and Affiliated to Rajasthan Technical University, Kota

Distributed Control Systems

A distributed control system (DCS) refers to a control system usually of a manufacturing system, process or any kind of dynamic system, in which the controller elements are not central in location (like the brain) but are distributed throughout the system with each component sub-system controlled by one or more controllers. The entire system of controllers is connected by networks for communication and monitoring.

History of Control Hardware

The DCS was introduced in 1975. Both Honeywell and Japanese electrical engineering firm Yokogawa introduced their own independently produced DCSs at roughly the same time, with the TDC 2000 and CENTUM[2] systems, respectively.

Computer Control Networks

OperatorControlPanel

MainControl

Computer

OperatorControlPanel

ArchivalData

Storage

Supervisory (host)Computer

PROCESS

LocalComputer

LocalComputer

LocalComputer

Local Display Local Display

Data highwayTo other Processes To other Processes

Local data acquisition andcontrol computers

DCS Elements-1

Local Control Unit: This unit can handle 8 to 16 individual PID loops.

Data Acquisition Unit: Digital (discrete) and analog I/O can be handle.

Batch Sequencing Unit: This unit controls a timing counters, arbitrary function generators, and internal logic.

Local Display: This device provides analog display stations, and video display for readout.

Bulk Memory Unit: This unit is used to store and recall process data.

DCS Elements-2

General Purpose Computer : This unit is programmed by a customer or third party to perform optimization, advance control, expert system, etc

Central Operator Display: This unit typically contain several consoles for operator communication with the system, and multiple video color graphics display units

Data Highway : A serial digital data transmission link connecting all other components in the system. It allow for redundant data highway to reduce the risk of data loss

Local area Network (LAN)

Advantages of Digital System

Digital computers are more flexible because they are programmable and no limitation to the complexity of the computations it can carry out.

Digital systems are more precise.

Digital system cost less to install and maintain Digital data in electronic files can be printed out,

displayed on color terminals, stored in highly compressed form.

Advantages of DCS

Access a large amount of current information from the data highway.

Monitoring trends of past process conditions.

Readily install new on-line measurements together with local computers.

Alternate quickly among standard control strategies and readjust controller parameters in software.

A sight full engineer can use the flexibility of the framework to implement his latest controller design ideas on the host computer.

Additional Advantage

Digital DCS systems are more flexible. Control algorithms can be changed and control configuration can be modified without having rewiring the system.

APPLICATIONS

• Distributed Control Systems (DCSs) are dedicated systems used to control manufacturing processes that are continuous or batch-oriented

• such as oil refining, petrochemicals, central station power generation, pharmaceuticals, food & beverage manufacturing, cement production, steelmaking, and papermaking.

HUMAN MACHINE INTERFACE

A Human-Machine Interface or HMI is the apparatus which presents process data to a human operator, and through which the human operator controls the process.

The HMI system usually presents the information to the operating personnel graphically, in the form of a mimic diagram. This means that the operator can see a schematic representation of the plant being controlled.

HMI CONTINUE.…

For example, a picture of a pump connected to a pipe can show the operator that the pump is running and how much fluid it is pumping through the pipe at the moment. The operator can then switch the pump off. The HMI software will show the flow rate of the fluid in the pipe decrease in real time. Mimic diagrams may consist of line graphics and schematic symbols to represent process elements, or may consist of digital photographs of the process equipment overlain with animated symbols.

HUMAN MACHINE INTERFACE

Interface between digital computer and analog instruments

(A/D) Transducers convert analog signals to digital signals. (Sensor Computer)

(D/A) Transducers convert digital signals to analog signals. (Computer Valve)

DCS Vendors

Honeywell Fisher-Rosemont Baily Foxboro Yokogawa Siemen

Thank You